Month: February 2012

If you know your way around a pool table you should be able to apply those skills to improving the sound of your home theater. [Eric Wolfram] put together a post that discusses the issues caused by unwanted sound reflections and shows how to position acoustic tiles to solve the problem.

This is a companion post to his guide on building your own acoustic tiles. Don’t worry if you haven’t gotten around to doing that yet. With just a wood frame, dense fiberglass, and some fabric they’re simple to build. They’re also easy to hang but until now you might have just guessed on where they should go.

Once you have all of your speakers and seats in position grab a mirror and some post-it notes. Take a seat as the viewer and have a friend operate the mirror as seen above. With it flat against the wall, mark each spot with a sticky-note where you can see a reflection of one of the speakers. Finding the reflection points is just like lining up a bank shot in Billiards. With five speakers (5.1 Surround Sound) and six surfaces (walls, ceiling, and floor) you should be able to mark 30 reflections points. Now decide how wild you plan to go with the project. The best result will address all 30 reflection points, but you can get by with just the front marks if you’re a bit more conservative.

[Vinod Stanur] just finished another hobby project by building a WAV audio player using a microcontroller. He had started development a while back using a PIC microcontroller. But the chip he was using didn’t have enough SRAM to allocate as a playback buffer. When he got his hands on an ATmega32 his mind turned back to the project and he saw it through to the end.

He takes advantage of what he learned on several earlier builds. He’s using a TV remote as input, just like his Snake game did. Storage is provided by an MMC card, a trick he perfected with this voice recorder project. Instead of using a FAT library, he uses his own code to read the linked-list (File Allocation Table) for sector addresses, then he parses the WAV header and processes the file accordingly.

Playback uses two 512 byte buffers. One is feeding the output while the other is being populated from the memory card. When the output buffer is exhausted the two are swapped and the process continues. You’ll find [Vinod’s] demo of the project after the break.

Wardriving started out as a search for unprotected WiFi access points before hot spots were prevalent. And so this ZigBee protocol wardriving hardware which [Travis Goodspeed] put together really gives us a sense of nostalgia for that time. Don’t get us wrong, we love our pervasive WiFi access and don’t wish to go back to simpler times. But if the radio signals your looking for are scarce, locating them provides a challenge.

Regular readers will recognize that [Travis] is interested in all things RF. One of his projects included sniffing wireless keyboard packets out of thin air and displaying them on the screen of his Nokia N900. This is right along those lines but he’s upgraded to an N9 phone for the display hardware. He switched up the RF hardware, using a TelosB (a board he’s already familiar with) to get on the 802.15.4 ZigBee spectrum. This dev board has an expansion port which let him use an RN42 module for wireless communications with the phone. This means the sniffing hardware can be hidden away in a backpack or jacket. After all, nobody will question someone walking around staring at a smart phone.

[John Philip’s] brother has a sizable room set aside for his model railroad setup, and he was looking for something interesting to add to his brother’s collection. Rather than construct something for the railroad itself, he decided that an early 1900’s-style semaphore railroad signal would make a great novelty item for the room.

The project started with [John] scouring the Internet for colored signal lenses. Once he found a set that worked for him, he crunched some numbers to ensure that the rest of the semaphore box stayed true to original scale. Inside the signal’s case you will find a small regulator board for his light source, an Arduino, and a motor controller board to actuate the arm.

To ensure that the signal arm is always perfectly positioned, he installed a pair of reed switches on either side of the case, enabling the Arduino to auto-calibrate the signal’s position each time it is powered on. At first, this control scheme might strike you as a bit over the top, but we really like the fact that the signal can always configure itself to function perfectly, even if someone tinkers with/bumps into/moves the arm at any point.

Be sure to stick around to see a short video of the semaphore signal in action.

The Earth orbits the Sun every 365.256 days. Because this number isn’t a whole number, an extra day is tacked onto February every four years, unless the year is evenly divisible by 100, except in cases where the year is divisible by 400, or something like that. To commemorate this calendar hack, here’s some stuff that has rolled in over the last week or so.

YouTube CLI

[Mike] uses YouTube as his music library. While this is a perfectly acceptable way to listen to music, the user interface is terrible. To solve this problem, [Mike] is downloading videos from the command line, automagically converting them to MP3, and playing them over speakers. It works well with SSH, so we’ll call this a win.

Key card lock

[valenitn] just joined the MIT Media Lab, but something was terribly wrong with his keys – an ID card was required to get into the building, but a key was necessary to get into his office. He doesn’t need the key anymore, at least since he modded his office door. Check out the video.

Not sure if brilliant or insane

[Vikash] ran across a forum post where a user named [I Shooter] describes his setup to dual-boot Windows and Linux: [I Shooter] connected data cables to a pair of SATA hard drives, one loaded up with Windows, the other with Linux. The power cables are switched using relays so only one drive is powered at a time. [I Shooter] gets a ton of points for creativity, but there’s a reason this brute force hardware dual-boot setup isn’t more common. We wish there were pictures of this one.

If you are thinking of building your own flight/racing sim setup at home, you might want to check this out. [Alex] from the Garoa Hackerspace in Säo Paulo, Brazil put together a slick setup that makes projector image calibration a breeze.

When building a wraparound screen for such a simulator, you are likely to run into problems with both overlapping images and distortion from the curved projection. There are projectors that can easily adjust themselves to work in this sort of setup, but they are often very expensive, so [Alex] thought he would build a solution himself.

Light sensors and an Arduino are attached to the back of the projection medium, and a large broad scan of the screen is performed by the projector. His code then triggers an additional sweep of each corner to better estimate the exact edges of his projection surface. Since the video is tweaked in software rather than relying on the projector hardware to handle the task, the result is cheap and very accurate.

Don’t take our word for it though, check out [Alex’s] video demonstration below to see his calibrator in action.

The Raspberry Pi has been launched. When we first heard of this board nearly a year ago, the idea of a $25 computer that displays 1080p video, runs Linux, and has enough ports to the outside world to do some very interesting stuff, we were cautiously optimistic. Now that the guys behind the Raspberry Pi are getting units out to the masses, we’re a little excited and also thinking about all the cool stuff we’re going to build.

The Raspberry Pi foundation is going with a licensed manufacturing setup with RS Components and Premier Farnell signing up to manufacture and distribute the boards. Right now it’s a strictly one-per-customer situation, but within a month or so you’ll be able to order as many as you would like.

Right now the foundation is focusing on the slightly more expensive ‘B’ model Raspberry Pi that includes Ethernet and USB over the $25 base unit. The ‘A’ model was originally slated to come with 128 MB of RAM, but due to some clever cost saving strategies, the team increased the base RAM to 256 MB.

Right now the only question we have is if an American distributor has signed on to sell this board; we’re sure something awesome will be built with this awesome little board. Commentors pointed out that Newarkwas selling Raspis for the US market, but they’re out of stock. The best advice may be to wait a few months for production to catch up to demand.